CAMBRIAN CHRONOSTRATIGAPHIC UNITS IN NORTH AMERICA

GSSPs of Cambrian chronostratigraphic units have focused on “FADs” (best termed LOs, Lowest Occurrences). The system’s top and bottom GSSPs are defined in North America (NAm). LOs of the eurytopic trace T. pedum are in the basal Cambrian transition globally. A GSSP modification (Landing et al., 2013) at disappearance of large Ediacaran taxa in the lower T. pedum range in Avalonian Newfoundland maintains the GSSP. The Ordovician GSSP (conodont Iapetognathus fluctivagus LO, W Newfoundland) is appropriate; a report that the form was not later recovered at the GSSP is at odds with early thorough documentation. This GSSP is somewhat “irrelevant;” the Ordovician base across most of Laurentia is an unconformity that truncates the C–O boundary interval. Subdivision of the Terreneuvian Series includes a proposed Stage 2 base at the rostroconch? Watsonella crosbyi LO in the I’ Excursion that is appropriate in Avalonian NAm (Laolingian Stage of Landing et al., 2013). Defining the Series 2 (Lenaldanian of Landing et al., 2013) and Stage 3 base at the “FAD of trilobites” is inappropriate: the group appeared 5+ m.y. earlier and has a globally diachronous LO. A Series 2 GSSP at onset of a d¹³C excursion (IV) in the lower range of Siberian trilobites brings the oldest Laurentian trilobites (California–Nevada) into Series 2. Little progress exists on a Series 2, Stage 4, GSSP, but assigning NAm Laurentian & Avalonian Calodiscus-Triangulaspis assemblages to Stage 4 is appropriate. High provinciality and definition in dysoxic facies mean imprecise correlation of higher Cambrian GSSPs into the Laurentian platform. The inadequate Wuliuan Stage GSSP, based on LO of distorted, facies-controlled (dysoxic) I. indicus in a chaotic (slumped) succession correlates above the Laurentian highest Olenellus Zone s.l. The basal Drumian (GSSP in Utah) and Guzhangian stages are best recognized in marginal (west) Laurentian successions. Correlation of the Paibian Stage into Laurentia is assisted by SPICE, and lower Jiangshanian Stage correlation into the Elvinia Z. is suggested by I. angustifolius. The Stage 10 GSSP alternatives are the LO of a dysoxic agnostoid with problematical taxonomy (“L. americanus”) and is unknown in Laurentia vs proposal of the LO of the eurytopic conodont E. notchpeakensis below the HERB Excursion onset (Landing et al., 2010).